CVE-2026-88378 in QuickJS
Summary
by MITRE • 09/24/2026
QuickJS commit 04be24600 contains a heap out-of-bounds write condition in JS_ReadFunctionTag().
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Analysis
by VulDB Data Team • 09/24/2026
The vulnerability identified within the QuickJS JavaScript engine, specifically addressed by commit 04be24600, represents a critical memory safety issue classified as a heap-based buffer overflow. This flaw resides within the JS_ReadFunctionTag function, which is responsible for parsing and deserializing serialized JavaScript functions during the import or loading of compiled bytecode. The core technical deficiency involves an insufficient validation check on array indices or length parameters derived from untrusted input data before they are used to write into a pre-allocated heap buffer. When the engine processes a maliciously crafted script, it fails to verify that the index calculated for writing function tag information remains within the bounds of the allocated memory region. This oversight allows an attacker to trigger a write operation beyond the end of the intended buffer structure on the heap.
From a technical perspective, this out-of-bounds write condition can lead to severe consequences including arbitrary code execution, denial of service through application crashes, or potential information disclosure depending on how adjacent memory is utilized by subsequent operations. Heap overflows are particularly dangerous because they corrupt metadata structures managed by the allocator, such as free lists or size fields, which can be exploited to gain control over program flow. In the context of QuickJS, since it is often embedded in various applications ranging from IoT devices to server-side runtimes and browser engines, this vulnerability poses a significant risk across multiple deployment scenarios where untrusted scripts might be executed.
The operational impact extends beyond simple application instability. An attacker who can inject or influence the serialized function data could potentially achieve remote code execution on the host system running the QuickJS instance. This is especially critical in environments that utilize sandboxing mechanisms, as a successful heap overflow may allow an escape from these restrictive boundaries if the corruption affects security-critical structures like exception handlers or virtual machine state objects. The lack of proper bounds checking means that even small discrepancies in input data can be leveraged to overwrite adjacent memory locations with controlled values, facilitating complex exploitation chains.
To mitigate this vulnerability, it is imperative for developers and maintainers to apply the patch included in commit 04be24600 immediately if they are using versions of QuickJS prior to this fix. The remediation involves implementing rigorous bounds checking within the JS_ReadFunctionTag function to ensure that all write operations remain strictly within the allocated buffer limits. Furthermore, adopting static analysis tools and fuzzing strategies during development can help identify similar memory safety issues early in the lifecycle. Organizations relying on QuickJS should also consider enabling AddressSanitizer or similar runtime error detection mechanisms in their testing environments to catch such violations before they reach production systems.
This vulnerability aligns with Common Weakness Enumeration (CWE) category CWE-787, which defines out-of-bounds write vulnerabilities involving heap memory. It is also relevant to the MITRE ATT&CK framework under techniques related to execution and privilege escalation via exploitation of binary vulnerabilities. By addressing this flaw through code updates and enhanced testing protocols, stakeholders can significantly reduce their attack surface against malicious script injection attacks targeting JavaScript engines embedded in modern software architectures.